One day I cycled back home from work when I suddenly found myself in a curious situation. Shimmering in the gutter lay a folded €20 bill. It was just lying there, between the fallen leaves, in front of one of those expensive homes that I passed by everyday. It was as if the bill called out to me: ‘Pick me up!’ I saw nobody coming from the house. But the road was quite busy with cyclists. There was a student a few meters behind me – I had just passed her – and I saw a man a little bit further behind me. I did not know the student, nor the man, who looked like a fellow academic.

I slowed down, and looked over my shoulder. The student and the man behind me slowed down too, but had not noticed the bill. I pulled over and picked it up. The student stopped cycling and got off her bike. The young woman looked me in the eye and smiled. I realized that I had been the lucky person to find the money, but that I was no more entitled to take it home than she was. “Is this yours?” I joked.

“Ehhm…no”, she said. Of course the money wasn’t hers. I had just asked her whether the money was hers to make me feel more entitled to take the money myself. It did not work. The money was not mine and I knew it. I had to find an excuse not to share the money. I bluffed. I held the bill in the air, made a ripping gesture and said: “We could split it…?” The man who was behind us had slowed down and looked at us. The student laughed and said: “Well, do you have a €10?” I realized I was trapped. Before I knew it I replied: “You never know”. I knew I did have a €10 bill in my wallet. I flipped it open, took out the €10 and gave it to her. The man frowned as he passed by. He certainly looked like an academic and seemed puzzled. I tucked away the €20 in my wallet. The student smiled and said “Thank you. Enjoy your day!” And I did. The sun shone brighter that day.

Later I realized that the incident with the money at broad daylight is curious not just because it was such a unique event. It was also curious because it is similar to a situation that I thought only existed in artificial experimental situations. Even on the day of the event I had been reading articles about ‘dictator game’ experiments. In these experiments, often conducted in psychological laboratories with students sitting alone in small cubicles, participants think they participate in a study on ‘decision making’ or ‘emotions’ but then suddenly get $10 in $1 bills. The students have not done anything to get the money. They just showed up at the right time at the right place, usually in exchange for a smaller ‘show up’ fee of $5. Their task in the experiment with the $10 is to decide how much of the $10 they would like to keep and how much they will give to an ‘anonymous other participant’. The receiver cannot refuse the money – that is why economists call the experiment a ‘Dictator Game’. The participant has the power to donate any desired amount, from $0 to $10. The payout happens in a separate room after the experiment. All participants enter the room individually and receive an envelope containing the money that their dictator has donated – if any. An ingenious procedure ensures that nobody (except the dictator, of course) will know who donated the money she receives. The recipient will not know who her dictator was.

Despite the unfavorable circumstances, participants in dictator games typically give away at least some of the money that they have received. In fact, the proportion of participants giving away nothing at all averages at a little over a third. Almost two thirds of the participants in these experiments donate at least $1. When I had first read about these experiments, I found the results fascinating and puzzling. Why would anyone give anything? There’s no punishment possible for not donating because the receiver has no power to refuse the money and because – except feelings of guilt. Without realizing that I had been in a real life dictator game, I had behaved as many students do in the laboratory.

Another reason why the incident with the money was curious was that it made me think again about theories on generosity that I had learned from reading articles in scientific journals. I thought I had gained some insights on why people give from these theories. But now that I had been in a real life dictator game, the ‘Generosity Puzzle’ seemed more difficult to solve. Why on earth do people give away money to people they don’t know? Why do people give money to people that they will probably never meet again, and who will not be able to give back what they have been given?

Because of the incident, these questions suddenly became personal questions. Why had I myself given away half of the money to a student that I did not know, and would probably never see again? Was it her smiling face when she asked whether I had a €10 bill? What if she had become angry with me and demanded half of the money? If she had not had the nerve to ask whether I had a €10 bill, I would probably have left with €20 instead of a €10. Or what if the student had been male? Would I have shared the money with him? And what if the man cycling behind us had joined our conversation? He had slowed down but had kept cycling. Though there is no easy way to split €20 into three equal amounts, there is also no good reason why the man had not asked for an equal share.

Perhaps a more remote influence had made me split the money with the student? Was it my parents who taught me the value of sharing? I remember a family holiday in Scandinavia with my parents and my brother when I was young. We paused on a parking lot and I walked around looking for stones. Suddenly I found three bills lying on the ground next to large truck. The money was a small fortune to me. Just as I had done when I found the €20 bill, I tried to find the owner, but there was nobody in the truck or anywhere on the parking lot. I gave the money to my mother. Upon our return to the parking lot at the end of the day, we found a parking fine on our car. The money I found went to the Oslo police.

Of course I also played a role in the event of the money myself. I could have just taken the money without saying anything. If I had not asked whether the money was hers, the student had probably gone home without any money from me. I offered to split the money because I felt lucky but not entitled to keep the money. You can keep money that you have worked for. If I had not endorsed this principle and if I had not felt lucky finding the money I would probably have kept it.

The incident of the money could have ended quite differently if the circumstances had been different and if the people involved had been different. Research on generosity shows that almost anything in the incident influenced the level of generosity that eventually took place. Though the incident was quite unique, it does share a fundamental property of generosity in being the product of a wide range of factors. It is not just the outcome of the values and personalities of the people involved – my gratitude, the justice principle, and the boldness of the student. Also more transient factors such as a good mood after a productive day’s work have an influence on generosity. Even seemingly meaningless characteristics of the situation such as the weather, the smile of a stranger and eye contact with a passer-by can have a profound impact on generosity. These factors have been studied by scholars in many different scientific disciplines who often work in mutual isolation. I hope my research efforts provide some useful pieces to the Generosity Puzzle.